1. Field of the Invention
This invention relates generally to a flow control valve for controlling the rate of flow of a gas used, for example, in the manufacture of semiconductors, and more particularly to a flow control valve suitable for use in a flow control system employing a piezoelectric actuator.
2. Description of the Related Art
Recently, in flow control valves of the type mentioned, a piezoelectric actuator has been used since it can finely control the flow rate. However, a piezoelectric actuator has a drawback in that the stroke is small, and therefore it has been difficult to obtain a flow control valve having a compact size and a large flow rate.
Therefore, projections of a complicated shape have heretofore been formed on a surface of a valve member and a valve seat member so as to achieve a large flow rate. Flow control valves employing such a construction are disclosed, for example, in Japanese Patent Public Disclosure Nos. 2-116071, 5-99349 and 62-24088.
However, these conventional flow control valves have problems that a valve member and other parts are complicated in construction, that the machining of these parts into their required configuration is rather difficult, that a great amount of time is required for their manufacture, and that the yield rate is low. Besides which, because of the complicated construction of the valve member and other parts, there has been encountered another problem that stresses are liable to develop, and therefore the working life of the valve is rather short, and a precisely closed condition of the valve can not be obtained.